A high lift system of an aircraft serves the purpose of lift and drag management for the aircraft. A high lift system is usually composed of a leading edge slat system and a trailing edge flap system. Many flap systems in civil and military aircraft are equipped with a central drive unit, which is also known as a power control unit (PCU), which drives a transmission shaft train and local mechanical actuator devices, the so-called drive stations, on corresponding flap support stations of the movable flaps. The high lift settings are selectable by a cockpit crew through a flaps lever, through which a flap angle is selectable.
The transmission system provides a load path from the central drive unit to all actuator outputs. This ensures a symmetrical deployment of all flap devices. Flap kinematics finally transform the rotary motion driven by the drive station, into required surface movements. The high lift flap system is usually controlled and monitored by two flap control computers. System drive commands primarily originate from a flaps lever input. The surfaces will be driven to a predetermined position that are laid down in the algorithms in the flap control computers. For achieving a high accuracy in driving the flap system to the predetermined position, flap drive system positions are continuously fed back by a feedback position pick-off unit (FPPU) attached to the drive unit and enabling smooth and accurate surface deployment. The feedback position pick-off unit is connected to the drive unit and comprises an internal gear-box to dedicate an equivalent system angle. In common high lift flap systems, the flap position is detected through the feedback position unit, wherein the working range of the feedback position pick-off unit is limited to one rotation (360°).
Further sensors are dedicated to system failure monitoring such as stations position pick-off units (SPPU), which are connected to individual drive stations to dedicate an equivalent angle for each station for system monitoring purposes.
In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.